1. Field of the Invention
This invention relates to a photoconductive member having sensitivity to electromagnetic waves such as light (herein used in a broad sense, including ultraviolet rays, visible light, infrared rays, x-rays, gamma-rays, and the like).
2. Description of the Prior Arts
Photoconductive materials, which constitute solid state image pick-up devices, image forming members for electrophotography in the field of image formation, or photoconductive layers in manuscript reading devices, are required to have a high sensitivity, a high SN ratio (Photocurrent (I.sub.p)/Dark current (I.sub.d)), spectral characteristics matching to those of electromagnetic waves to be irradiated, a rapid response to light, a desired dark resistance value as well as no harm to human bodies during usage. Further, in a solid state image pick-up device, it is also required that the residual image should easily be treated within a predetermined time. In particular, in case of an image forming member for electrophotography to be assembled in an electrophotographic device to be used in an office as office apparatus, the aforesaid harmless characteristic is very important.
From the standpoint as mentioned above, amorphous silicon (hereinafter referred to as a-Si) has recently attracted attention as a photoconductive material. For example, German Laid-Open Patent Publication Nos. 2746967 and 2855718 disclose applications of a-Si for use in image forming members for electrophotography, and German Laid-Open Patent Publication No. 2933411 an application of a-Si for use in a photoelectroconverting reading device.
However, under the present situation, the photoconductive members having photoconductive layers constituted of a conventional a-Si are further required to be improved in various aspects including electrical, optical and photoconductive characteristics such as dark resistance value, photosensitivity and response to light, etc., and environmental characteristics during use, further stability with lapse of time, and durability.
For instance, when applied in an image forming member for electrophotography, residual potential is frequently observed to remain during use thereof if improvements to higher photosensitivity and higher dark resistance are scheduled to be effected at the same time. When such a photoconductive member is repeatedly used for a long time, there will be caused various inconveniences such as accumulation of fatigues by repeated uses or so called ghost phenomenon wherein residual images are formed.
Further, a-Si materials may contain as constituent atoms hydrogen atoms or halogen atoms such as fluorine atoms, chlorine atoms. etc. for improving their electrical, photoconductive characteristics, boron atoms, phosphorous atoms, etc. for controlling the electroconduction type as well as other atoms for improving other characteristics. Depending on the manner in which these constituent atoms are contained, there may sometimes be caused problems with respect to electrical, photoconductive characteristics or dielectric strength, and further durability of the layer formed.
That is, for example, in many cases, the life of the photocarriers generated by light irradiation in the photoconductive layer formed is insufficient, or at the dark portion, the charges injected from the support side cannot sufficiently be impeded.
Further, when the layer thickness becomes ten and several microns, there is a tendency to cause such phenomena as loosening or peeling of the layer off from the surface of the support or formation of cracks in the layer with lapse of time when left to stand in the air after taken out from the vacuum deposition chamber for layer formation. These phenomena will occur frequently particularly in case of a drum-shaped support to be used conventionally in the field of electrophotography. Thus, there is the problem to be solved with respect to stability with lapse of time.
Thus, it is required in designing of a photoconductive material to make efforts to solve the above-mentioned problems along wih the improvement of a-Si materials per se.
In view of the above points, the present invention contemplates the achievement obtained as a result of extensive studies made comprehensively from the standpoints of applicability and utility of a-Si as a photoconductive member for image forming members for electrophotography, solid state image pick-up devices, reading devices, etc. It has now been found that a photoconductive member having a photoconductive layer comprising an amorphous layer exhibiting photoconductivity, which is constituted of so-called hydrogenated amorphous silicon, halogenated amorphous silicon or halogen-containing hydrogenated amorphous silicon which is an amorphous material containing at least one of hydrogen atom (H) and halogen atom (X) in a matrix of a-Si, especially silicon atoms (hereinafter referred to comprehensively as a-Si(H,X)), said photoconductive member being prepared by designing so as to have a specific structure, is found to exhibit not only practically extremely excellent characteristics but also surpass the photoconductive members of the prior art in substantially all respects, especially markedly excellent characteristics as a photoconductive member for electrophotography. The present invention is based on such finding.